U.S. networks pumped out the highest percentage of attacks during the second half of last year, with China running a distant second, according to a report released Monday by security firm Symantec.
The U.S. accounted for 31 percent of malicious activity originating from computer networks, while 10 percent came from China and 7 percent from Germany, Symantec said in its Internet Security Threat Report.
The company also found that 51 percent of all known servers used by attackers to buy or sell stolen personal information, such as credit card or bank account numbers, are located in the U.S.

U.S.-based credit cards, with accompanying verification numbers, were found to be selling for $1 to $6 each on these servers. But a more thorough roundup of personal-identification data--including a person's birthdate and banking, credit card and government-issued identification numbers--fetched $14 to $18, the report noted.

Internet thieves increasingly are turning to Trojan-horse software, which can load keylogging software onto unsuspecting victims' computers. The software is able to harvest people's log-in names and passwords to various accounts and can glean other sensitive information people type into their computers.